The present invention relates to a push switch used in portable electronic devices including a cellular phone, a headphone stereo cassette and the like.
Recently, portable electronic devices have been downsized and thinned remarkably. Thus, the demand for the push switches used in these portable electronic devices to also be downsized and thinned has been strong.
A conventional push switch is described hereinafter with reference to FIGS. 14 and 15. FIG. 14 is a front cross sectional view of the conventional push switch. FIG. 15 is a plan view of a switch housing illustrating a fixed contact of the switch shown in FIG. 14.
The conventional push switch shown in FIGS. 14 and 15 comprises a switch housing 1 shaped as a box and made of insulated resin, a central fixed contact 2 disposed at the center of a bottom face of a recess in switch housing 1, coupling terminals 2A, 2B extending from the central fixed contact 2 to the outside of switch housing 1, an outside fixed contact 3 disposed on a periphery of the recess of switch housing 1, coupling terminals 3A, 3B extending from the outside fixed contact 3 to the outside of switch housing 1, a domed movable contact 4 bowed upwardly, made of a thin metallic plate and accommodated in the recess so that its outer rim is placed on outside-fixed-contact 3 of switch housing 1, and a flexible film 5 covering the recess which accommodates domed-movable contact 4.
Coupling, terminals 2A, 2B, 3A and 3B are insert-molded with switch housing 1 and led outside the housing 1. Film 5 has bonding agent 5A on its lower face. Film 5 adheres to upper face of the periphery of the recess due to bonding agent 5A. A small and thin push switch is thus structured.
An operation of the push switch structured above is described hereinafter. First, film 5 is depressed downwardly, then top section 4A of domed movable contact 4 is bent and elastically deformed. This elastic deformation brings top section 4A into contact with central fixed contact 2. Therefore, outside fixed contact 3 becomes electrically connected to central fixed contact 2 via domed movable contact 4. In other words, the push switch is turned on. When the depressing force is removed, movable contact 4 restores itself to an original place shown in FIG. 14 due to its elastic restoring force (i.e., the push switch is turned off).
However, in the conventional push switch discussed above, coupling terminals 2A, 2B are electrically connected to the central fixed contact, and coupling terminal 3A, 3B are electrically connected to the outside fixed contact. These four terminals 2A, 2B, 3A and 3B are led outside switch housing 1. When the conventional push switch is mounted onto a printed wired board, a wiring for the push switch must be coupled to at least one of terminals 2A and 2B. In the same manner, the wiring also must be coupled to at least one of terminals 3A and 3B. Thus, the circuit wiring is routed with some restrictions in a design stage. As a result, when a-printed-wiring-circuit including the conventional push switch is designed, a subject electronic device to be designed encounters restrictions of downsizing and thinning.
The present invention addresses the problem discussed above, and aims to provide a push switch which allows increased flexibility in the design of a printed wiring board. As a result, restrictions in the design of a thin and compact electronic device can be reduced.
To achieve the object, the push switch of the present invention includes at least three fixed contacts disposed electrically independently on a bottom face at a recess of a switch housing shaped as a box and made of insulated resin. Coupling terminals extend from these fixed contacts and are led out externally, and contact-receptors are provided at corners of the bottom face of the recess. A domed movable contact has a center section which is bowed upwardly, and the movable contact is placed on the contact-receptors and accommodated in the recess of the switch housing, and a lid covers the recess and is fixed to the switch housing.
When the push switch structured above is depressed, the domed movable contact is reversed and brought into contact with the plural fixed contacts simultaneously. Therefore, two random coupling terminals led out from the plural fixed contacts can have a switch function. As a result, a push switch, which allows increased flexibility in the design of a printed wiring board and reduces restrictions in the design of a thin and compact electronic device, is obtainable.